In a case where products such as medicine and food are transported or stored, in some cases, a sensor for recording a management state such as a temperature or humidity is attached to product main bodies, a box for transport, a truck for transport, or the like in order to guarantee quality of the products. A kind of sensor for recording a management state is a sensor-function-equipped mark. As a method of reading this sensor-function-equipped mark, there are two types of methods, i.e., visual observation by a human and reading by a machine. A sensor-function-equipped mark read by visual observation is advantageous in that a manager or consumer can determine normality or abnormality of a management state without using a machine. Meanwhile, a sensor-function-equipped mark read by a machine, such as a barcode or a matrix-type two-dimensional code, is advantageous in that data can be formed because the sensor-function-equipped mark is read by a machine. Those sensor-function-equipped marks are required to, in a case where abnormality of a management state is detected, warn a manager or consumer about abnormality of a product by changing color, shapes, or the like.
PTL 1 discloses a technology of recording a management state of a temperature by using a mark that is suitable for reading by visual observation and is printed in a temperature-indicating ink in the vicinity of a barcode attached to a package of food. In this technology, in a case where a temperature of a product becomes equal to or more than a prescribed temperature, color of the mark is changed so that the mark warns a manager or consumer of the product.
PTL 2 discloses a technology of recording a management state of a temperature by using a plurality of barcodes printed in a temperature-indicating ink. In this technology, readability/unreadability of each barcode is switched in a different temperature zone. Therefore, it is possible to determine the highest and lowest temperatures during transport and storage by reading a readable mark for machine reading.